O.k.... I've got a 89 2+0, it was a NA Auto, My mechanic just finished fitting the TT engine and manual gear box, all was going great, he was just about to ring me to tell me to come and pick it up when he decided to take her for one more spin around the block. Thats when it all went bad, engine would fire then stop, fire then stop, eventually not firing at all, after hours of going over it (fuel, spark, injector pulses, etc.) he came to the conclusion it had to be the ecu, so out of desperation he put the NA ecu back in and it ran! rough as hell of coarse but it ran. i got on the phone and got another TT ecu sent up to him, he installed that one and it ran fine, he put it up on the rollers, gave it a tune and all was good! While it was up on the rollers just idling it stopped again, same thing again, just fires up then stops. (He swapped Ptu from the NA engine, it has TT fuel pump). has anyone experienced anything like this?
Bad earth somewhere I reckon. $10 you've fried another ECU Get him to check all the earths are connected, plenum, gearbox, chassis etc.
Possible. You have to think of what was fiddled with when the engine was changed. It's nearly all mechanical. Only thing that is really left is ECU, loom and earths. The ECU is a easy swap, can't really stuff it up. Loom may have been damaged from being pushed out of the way. What sort of condition was it in? Nice and soft or did it make crack noises if you try and bend it a bit? It's REALLY easy to miss a earth or two when you're putting a engine back in. If you have missed a earth then you may be trying to switch more current though the ECU than it can handle. It gets a bit hot after a while then *Poof* it's dead. It's possible that the PTU is the culprit. When the S1 are going out they often work when cold then conk out when they get hot. I don't know how long this 'tune' was, if it was only a few mins then that could be the issue, if it was a 'proper' tune going for a few hours then probably not. Any error codes being thrown?
i dont think the second tune was a proper tune, i think it stopped before before he finished. i forgot to ask about error codes. he is racing tomorrow but ill get back to see him on Saturday. My first thought was the earths, and when i asked about the PTU he said he had Tried the one off the NA engine.So the common factor is still the earths isnt it?
Yeah it certainly sounds like the problem, the TT loom was also swapped in with the conversion so there would probably be a handful of chassis earth's to account for as well as the engine earth's. Dam, guess i'll be lookin for another ecu tomorrow.
I fried both the ECU and AFM on a Volvo once when the chassis to engine earth cable broke. Power to the starter went through the ECU and killed it.
The earth points are: Batt neg to body(near battery) This same cable then earths to the back of the left hand cylinder head and then on to one of the gearbox bolts. There is and earth cable from the back of the gearbox to one of the g/box crossmember bolts. The EFI harness has 3 small earths that are bolted to the plenum, 2 of these are bolted near the iacv, the other one is bolted on the back of the #5 intake runner. The ecu interanals are above ground, meaning the internals are not grounded through the ecu body, and are earthed through the one at #5 intake runner. If it fails ecu's, this wire may not be connected or is open circuit back to the ecu. The other 2 small wires if not earthed will fail the ptu or ignition drivers in the ecu. There is also a junction in the harness about 6 inches from the ecu connector that joins the ecu earth circuits to one single wire. This may have been upset when the ecu was changed over. If it runs for about 5mins or so and then stops it will be the ptu, possibly caused by the 2 small wires earthed near the iacv. If it runs for a while before stopping, then suspect ecu failure from poor ecu earth circuits. Another possiblity is ptu harness rubbing on the power steer pulley or belt, this will cause intermittent shorts to gound in the ecu ignition driver circuitry. Before any parts are changed check the alt output, if it is too high it may cause an overload in the ecu.
